The acid–base behaviour of hexamine and its N-acetyl derivatives
The protonation equilibria and decomposition reactions in aqueous hydrochloric acid of hexamine and its acylated derivatives (2), (3), and (4) have been examined by u.v. and 1H n.m.r. spectroscopy. pKa Values at 25 °C are: hexamine 4.89, 3,7-diacetyl-1,3,5,7-tetra-azabicyclo[18.104.22.168]nonane (DAPT) 0.7, 1,3,5,7-tetra-acetyl-1,3,5,7-tetra-azacyclo-octane (TAT)-2.5, and 1,3,5-triacelyl-1,3,5-triaza cyclohexane (TRAT)–2.3. Rates of decomposition of the protonated substrates decrease in the order DAPT > TAT > hexamine.
Reaction of hexamine with picryl acetate may involve nucleophilic catalysis via the N-acetylhexaminium cation (6).